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<h1><span class="logo-braces">{ }</span> <a href="http://codemirror.net/">CodeMirror</a></h1>

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<img src="baboon.png" class="logo" alt="logo"/>
<pre>
/* User manual and
   reference guide */
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<div class="clear"><div class="leftbig blk">

    <h2 id="overview">Overview</h2>

    <p>CodeMirror is a code-editor component that can be embedded in
    Web pages. The core library provides <em>only</em> the editor
    component, no accompanying buttons, auto-completion, or other IDE
    functionality. It does provide a rich API on top of which such
    functionality can be straightforwardly implemented. See
    the <a href="#addons">add-ons</a> included in the distribution,
    and
    the <a href="https://github.com/jagthedrummer/codemirror-ui">CodeMirror
    UI</a> project, for reusable implementations of extra features.</p>

    <p>CodeMirror works with language-specific modes. Modes are
    JavaScript programs that help color (and optionally indent) text
    written in a given language. The distribution comes with a number
    of modes (see the <a href="../mode/"><code>mode/</code></a>
    directory), and it isn't hard to <a href="#modeapi">write new
    ones</a> for other languages.</p>

    <h2 id="usage">Basic Usage</h2>

    <p>The easiest way to use CodeMirror is to simply load the script
    and style sheet found under <code>lib/</code> in the distribution,
    plus a mode script from one of the <code>mode/</code> directories.
    (See <a href="compress.html">the compression helper</a> for an
    easy way to combine scripts.) For example:</p>

    <pre data-lang="text/html">&lt;script src="lib/codemirror.js">&lt;/script>
&lt;link rel="stylesheet" href="../lib/codemirror.css">
&lt;script src="mode/javascript/javascript.js">&lt;/script></pre>

    <p>Having done this, an editor instance can be created like
    this:</p>

    <pre data-lang="javascript">var myCodeMirror = CodeMirror(document.body);</pre>

    <p>The editor will be appended to the document body, will start
    empty, and will use the mode that we loaded. To have more control
    over the new editor, a configuration object can be passed
    to <code>CodeMirror</code> as a second argument:</p>

    <pre data-lang="javascript">var myCodeMirror = CodeMirror(document.body, {
  value: "function myScript(){return 100;}\n",
  mode:  "javascript"
});</pre>

    <p>This will initialize the editor with a piece of code already in
    it, and explicitly tell it to use the JavaScript mode (which is
    useful when multiple modes are loaded).
    See <a href="#config">below</a> for a full discussion of the
    configuration options that CodeMirror accepts.</p>

    <p>In cases where you don't want to append the editor to an
    element, and need more control over the way it is inserted, the
    first argument to the <code>CodeMirror</code> function can also
    be a function that, when given a DOM element, inserts it into the
    document somewhere. This could be used to, for example, replace a
    textarea with a real editor:</p>

    <pre data-lang="javascript">var myCodeMirror = CodeMirror(function(elt) {
  myTextArea.parentNode.replaceChild(elt, myTextArea);
}, {value: myTextArea.value});</pre>

    <p>However, for this use case, which is a common way to use
    CodeMirror, the library provides a much more powerful
    shortcut:</p>

    <pre data-lang="javascript">var myCodeMirror = CodeMirror.fromTextArea(myTextArea);</pre>

    <p>This will, among other things, ensure that the textarea's value
    is updated with the editor's contents when the form (if it is part
    of a form) is submitted. See the <a href="#fromTextArea">API
    reference</a> for a full description of this method.</p>

    <h2 id="config">Configuration</h2>

    <p>Both the <code>CodeMirror</code> function and
    its <code>fromTextArea</code> method take as second (optional)
    argument an object containing configuration options. Any option
    not supplied like this will be taken
    from <code>CodeMirror.defaults</code>, an object containing the
    default options. You can update this object to change the defaults
    on your page.</p>

    <p>Options are not checked in any way, so setting bogus option
    values is bound to lead to odd errors.</p>

    <p>These are the supported options:</p>

    <dl>
      <dt id="option_value"><code>value (string or Doc)</code></dt>
      <dd>The starting value of the editor. Can be a string, or
      a <a href="#api_doc">document object</a>.</dd>

      <dt id="option_mode"><code>mode (string or object)</code></dt>
      <dd>The mode to use. When not given, this will default to the
      first mode that was loaded. It may be a string, which either
      simply names the mode or is
      a <a href="http://en.wikipedia.org/wiki/MIME">MIME</a> type
      associated with the mode. Alternatively, it may be an object
      containing configuration options for the mode, with
      a <code>name</code> property that names the mode (for
      example <code>{name: "javascript", json: true}</code>). The demo
      pages for each mode contain information about what configuration
      parameters the mode supports. You can ask CodeMirror which modes
      and MIME types have been defined by inspecting
      the <code>CodeMirror.modes</code>
      and <code>CodeMirror.mimeModes</code> objects. The first maps
      mode names to their constructors, and the second maps MIME types
      to mode specs.</dd>

      <dt id="option_theme"><code>theme (string)</code></dt>
      <dd>The theme to style the editor with. You must make sure the
      CSS file defining the corresponding <code>.cm-s-[name]</code>
      styles is loaded (see
      the <a href="../theme/"><code>theme</code></a> directory in the
      distribution). The default is <code>"default"</code>, for which
      colors are included in <code>codemirror.css</code>. It is
      possible to use multiple theming classes at once—for
      example <code>"foo bar"</code> will assign both
      the <code>cm-s-foo</code> and the <code>cm-s-bar</code> classes
      to the editor.</dd>

      <dt id="option_indentUnit"><code>indentUnit (integer)</code></dt>
      <dd>How many spaces a block (whatever that means in the edited
      language) should be indented. The default is 2.</dd>

      <dt id="option_smartIndent"><code>smartIndent (boolean)</code></dt>
      <dd>Whether to use the context-sensitive indentation that the
      mode provides (or just indent the same as the line before).
      Defaults to true.</dd>

      <dt id="option_tabSize"><code>tabSize (integer)</code></dt>
      <dd>The width of a tab character. Defaults to 4.</dd>

      <dt id="option_indentWithTabs"><code>indentWithTabs (boolean)</code></dt>
      <dd>Whether, when indenting, the first N*<code>tabSize</code>
      spaces should be replaced by N tabs. Default is false.</dd>

      <dt id="option_electricChars"><code>electricChars (boolean)</code></dt>
      <dd>Configures whether the editor should re-indent the current
      line when a character is typed that might change its proper
      indentation (only works if the mode supports indentation).
      Default is true.</dd>

      <dt id="option_rtlMoveVisually"><code>rtlMoveVisually (boolean)</code></dt>
      <dd>Determines whether horizontal cursor movement through
      right-to-left (Arabic, Hebrew) text is visual (pressing the left
      arrow moves the cursor left) or logical (pressing the left arrow
      moves to the next lower index in the string, which is visually
      right in right-to-left text). The default is <code>false</code>
      on Windows, and <code>true</code> on other platforms.</dd>

      <dt id="option_keyMap"><code>keyMap (string)</code></dt>
      <dd>Configures the keymap to use. The default
      is <code>"default"</code>, which is the only keymap defined
      in <code>codemirror.js</code> itself. Extra keymaps are found in
      the <a href="../keymap/"><code>keymap</code></a> directory. See
      the <a href="#keymaps">section on keymaps</a> for more
      information.</dd>

      <dt id="option_extraKeys"><code>extraKeys (object)</code></dt>
      <dd>Can be used to specify extra keybindings for the editor,
      alongside the ones defined
      by <a href="#option_keyMap"><code>keyMap</code></a>. Should be
      either null, or a valid <a href="#keymaps">keymap</a> value.</dd>

      <dt id="option_lineWrapping"><code>lineWrapping (boolean)</code></dt>
      <dd>Whether CodeMirror should scroll or wrap for long lines.
      Defaults to <code>false</code> (scroll).</dd>

      <dt id="option_lineNumbers"><code>lineNumbers (boolean)</code></dt>
      <dd>Whether to show line numbers to the left of the editor.</dd>

      <dt id="option_firstLineNumber"><code>firstLineNumber (integer)</code></dt>
      <dd>At which number to start counting lines. Default is 1.</dd>

      <dt id="option_lineNumberFormatter"><code>lineNumberFormatter (function)</code></dt>
      <dd>A function used to format line numbers. The function is
      passed the line number, and should return a string that will be
      shown in the gutter.</dd>

      <dt id="option_gutters"><code>gutters (array)</code></dt>
      <dd>Can be used to add extra gutters (beyond or instead of the
      line number gutter). Should be an array of CSS class names, each
      of which defines a <code>width</code> (and optionally a
      background), and which will be used to draw the background of
      the gutters. <em>May</em> include
      the <code>CodeMirror-linenumbers</code> class, in order to
      explicitly set the position of the line number gutter (it will
      default to be to the right of all other gutters). These class
      names are the keys passed
      to <a href="#setGutterMarker"><code>setGutterMarker</code></a>.</dd>

      <dt id="option_fixedGutter"><code>fixedGutter (boolean)</code></dt>
      <dd>Determines whether the gutter scrolls along with the content
      horizontally (false) or whether it stays fixed during horizontal
      scrolling (true, the default).</dd>

      <dt id="option_readOnly"><code>readOnly (boolean)</code></dt>
      <dd>This disables editing of the editor content by the user. If
      the special value <code>"nocursor"</code> is given (instead of
      simply <code>true</code>), focusing of the editor is also
      disallowed.</dd>

      <dt id="option_showCursorWhenSelecting"><code>showCursorWhenSelecting (boolean)</code></dt>
      <dd>Whether the cursor should be drawn when a selection is
      active. Defaults to false.</dd>

      <dt id="option_undoDepth"><code>undoDepth (integer)</code></dt>
      <dd>The maximum number of undo levels that the editor stores.
      Defaults to 40.</dd>

      <dt id="option_tabindex"><code>tabindex (integer)</code></dt>
      <dd>The <a href="http://www.w3.org/TR/html401/interact/forms.html#adef-tabindex">tab
      index</a> to assign to the editor. If not given, no tab index
      will be assigned.</dd>

      <dt id="option_autofocus"><code>autofocus (boolean)</code></dt>
      <dd>Can be used to make CodeMirror focus itself on
      initialization. Defaults to off.
      When <a href="#fromTextArea"><code>fromTextArea</code></a> is
      used, and no explicit value is given for this option, it will be
      set to true when either the source textarea is focused, or it
      has an <code>autofocus</code> attribute and no other element is
      focused.</dd>
    </dl>

    <p>Below this a few more specialized, low-level options are
    listed. These are only useful in very specific situations, you
    might want to skip them the first time you read this manual.</p>

    <dl>
      <dt id="option_dragDrop"><code>dragDrop (boolean)</code></dt>
      <dd>Controls whether drag-and-drop is enabled. On by default.</dd>

      <dt id="option_onDragEvent"><code>onDragEvent (function)</code></dt>
      <dd>When given, this will be called when the editor is handling
      a <code>dragenter</code>, <code>dragover</code>,
      or <code>drop</code> event. It will be passed the editor instance
      and the event object as arguments. The callback can choose to
      handle the event itself, in which case it should
      return <code>true</code> to indicate that CodeMirror should not
      do anything further.</dd>

      <dt id="option_onKeyEvent"><code>onKeyEvent (function)</code></dt>
      <dd>This provides a rather low-level hook into CodeMirror's key
      handling. If provided, this function will be called on
      every <code>keydown</code>, <code>keyup</code>,
      and <code>keypress</code> event that CodeMirror captures. It
      will be passed two arguments, the editor instance and the key
      event. This key event is pretty much the raw key event, except
      that a <code>stop()</code> method is always added to it. You
      could feed it to, for example, <code>jQuery.Event</code> to
      further normalize it.<br>This function can inspect the key
      event, and handle it if it wants to. It may return true to tell
      CodeMirror to ignore the event. Be wary that, on some browsers,
      stopping a <code>keydown</code> does not stop
      the <code>keypress</code> from firing, whereas on others it
      does. If you respond to an event, you should probably inspect
      its <code>type</code> property and only do something when it
      is <code>keydown</code> (or <code>keypress</code> for actions
      that need character data).</dd>

      <dt id="option_cursorBlinkRate"><code>cursorBlinkRate (number)</code></dt>
      <dd>Half-period in milliseconds used for cursor blinking. The default blink
      rate is 530ms.</dd>

      <dt id="option_cursorHeight"><code>cursorHeight (number)</code></dt>
      <dd>Determines the height of the cursor. Default is 1, meaning
      it spans the whole height of the line. For some fonts (and by
      some tastes) a smaller height (for example <code>0.85</code>),
      which causes the cursor to not reach all the way to the bottom
      of the line, looks better</dd>

      <dt id="option_workTime"><code>workTime, workDelay (number)</code></dt>
      <dd>Highlighting is done by a pseudo background-thread that will
      work for <code>workTime</code> milliseconds, and then use
      timeout to sleep for <code>workDelay</code> milliseconds. The
      defaults are 200 and 300, you can change these options to make
      the highlighting more or less aggressive.</dd>

      <dt id="option_pollInterval"><code>pollInterval (number)</code></dt>
      <dd>Indicates how quickly CodeMirror should poll its input
      textarea for changes (when focused). Most input is captured by
      events, but some things, like IME input on some browsers, don't
      generate events that allow CodeMirror to properly detect it.
      Thus, it polls. Default is 100 milliseconds.</dd>

      <dt id="option_flattenSpans"><code>flattenSpans (boolean)</code></dt>
      <dd>By default, CodeMirror will combine adjacent tokens into a
      single span if they have the same class. This will result in a
      simpler DOM tree, and thus perform better. With some kinds of
      styling (such as rounded corners), this will change the way the
      document looks. You can set this option to false to disable this
      behavior.</dd>

      <dt id="option_viewportMargin"><code>viewportMargin (integer)</code></dt>
      <dd>Specifies the amount of lines that are rendered above and
      below the part of the document that's currently scrolled into
      view. This affects the amount of updates needed when scrolling,
      and the amount of work that such an update does. You should
      usually leave it at its default, 10. Can be set
      to <code>Infinity</code> to make sure the whole document is
      always rendered, and thus the browser's text search works on it.
      This <em>will</em> have bad effects on performance of big
      documents.</dd>
    </dl>

    <h2 id="events">Events</h2>

    <p>A CodeMirror instance emits a number of events, which allow
    client code to react to various situations. These are registered
    with the <a href="#on"><code>on</code></a> method (and
    removed with the <a href="#off"><code>off</code></a>
    method). These are the events that fire on the instance object.
    The name of the event is followed by the arguments that will be
    passed to the handler. The <code>instance</code> argument always
    refers to the editor instance.</p>

    <dl>
      <dt id="event_change"><code>"change" (instance, changeObj)</code></dt>
      <dd>Fires every time the content of the editor is changed.
      The <code>changeObj</code> is a <code>{from, to, text, removed,
      next}</code> object containing information about the changes
      that occurred as second argument. <code>from</code>
      and <code>to</code> are the positions (in the pre-change
      coordinate system) where the change started and ended (for
      example, it might be <code>{ch:0, line:18}</code> if the
      position is at the beginning of line #19). <code>text</code> is
      an array of strings representing the text that replaced the
      changed range (split by line). <code>removed</code> is the text
      that used to be between <code>from</code> and <code>to</code>,
      which is overwritten by this change. If multiple changes
      happened during a single operation, the object will have
      a <code>next</code> property pointing to another change object
      (which may point to another, etc).</dd>

      <dt id="event_beforeChange"><code>"beforeChange" (instance, change)</code></dt>
      <dd>This event is fired before a change is applied, and its
      handler may choose to modify or cancel the change.
      The <code>change</code> object
      has <code>from</code>, <code>to</code>, and <code>text</code>
      properties, as with
      the <a href="#event_change"><code>"change"</code></a> event, but
      never a <code>next</code> property, since this is fired for each
      individual change, and not batched per operation. It also
      has <code>update(from, to, text)</code>
      and <code>cancel()</code> methods, which may be used to modify
      or cancel the change. All three arguments to <code>update</code>
      are optional, and can be left off to leave the existing value
      for that field intact. <strong>Note:</strong> you may not do
      anything from a <code>"beforeChange"</code> handler that would
      cause changes to the document or its visualization. Doing so
      will, since this handler is called directly from the bowels of
      the CodeMirror implementation, probably cause the editor to
      become corrupted.</dd>

      <dt id="event_cursorActivity"><code>"cursorActivity" (instance)</code></dt>
      <dd>Will be fired when the cursor or selection moves, or any
      change is made to the editor content.</dd>

      <dt id="event_beforeSelectionChange"><code>"beforeSelectionChange" (instance, selection)</code></dt>
      <dd>This event is fired before the selection is moved. Its
      handler may modify the resulting selection head and anchor.
      The <code>selection</code> parameter is an object
      with <code>head</code> and <code>anchor</code> properties
      holding <code>{line, ch}</code> objects, which the handler can
      read and update. Handlers for this event have the same
      restriction
      as <a href="#event_beforeChange"><code>"beforeChange"</code></a>
      handlers — they should not do anything to directly update the
      state of the editor.</dd>

      <dt id="event_viewportChange"><code>"viewportChange" (instance, from, to)</code></dt>
      <dd>Fires whenever the <a href="#getViewport">view port</a> of
      the editor changes (due to scrolling, editing, or any other
      factor). The <code>from</code> and <code>to</code> arguments
      give the new start and end of the viewport.</dd>

      <dt id="event_gutterClick"><code>"gutterClick" (instance, line, gutter, clickEvent)</code></dt>
      <dd>Fires when the editor gutter (the line-number area) is
      clicked. Will pass the editor instance as first argument, the
      (zero-based) number of the line that was clicked as second
      argument, the CSS class of the gutter that was clicked as third
      argument, and the raw <code>mousedown</code> event object as
      fourth argument.</dd>

      <dt id="event_focus"><code>"focus", "blur" (instance)</code></dt>
      <dd>These fire whenever the editor is focused or unfocused.</dd>

      <dt id="event_scroll"><code>"scroll" (instance)</code></dt>
      <dd>Fires when the editor is scrolled.</dd>

      <dt id="event_update"><code>"update" (instance)</code></dt>
      <dd>Will be fired whenever CodeMirror updates its DOM display.</dd>

      <dt id="event_renderLine"><code>"renderLine" (instance, line, element)</code></dt>
      <dd>Fired whenever a line is (re-)rendered to the DOM. Fired
      right after the DOM element is built, <em>before</em> it is
      added to the document. The handler may mess with the style of
      the resulting element, or add event handlers, but
      should <em>not</em> try to change the state of the editor.</dd>
    </dl>

    <p>It is also possible to <a href="#on">register</a> events on
    other objects. Use <code>CodeMirror.on(handle, "eventName",
    func)</code> to register handlers on objects that don't have their
    own <code>on</code> method. Document objects (instances
    of <a href="#Doc"><code>CodeMirror.Doc</code></a>) emit the
    following events:</p>

    <dl>
      <dt id="event_doc_change"><code>"change" (doc, changeObj)</code></dt>
      <dd>Fired whenever a change occurs to the
      document. <code>changeObj</code> has a similar type as the
      object passed to the
      editor's <a href="#event_change"><code>"change"</code></a>
      event, but it never has a <code>next</code> property, because
      document change events are not batched (whereas editor change
      events are).</dd>

      <dt id="event_doc_beforeChange"><code>"beforeChange" (doc, change)</code></dt>
      <dd>See the <a href="#event_beforeChange">description of the
      same event</a> on editor instances.</dd>

      <dt id="event_doc_cursorActivity"><code>"cursorActivity" (doc)</code></dt>
      <dd>Fired whenever the cursor or selection in this document
      changes.</dd>

      <dt id="event_doc_beforeSelectionChange"><code>"beforeSelectionChange" (doc, selection)</code></dt>
      <dd>Equivalent to
      the <a href="#event_beforeSelectionChange">event by the same
      name</a> as fired on editor instances.</dd>
    </dl>

    <p>Line handles (as returned by, for
    example, <a href="#getLineHandle"><code>getLineHandle</code></a>)
    support these events:</p>

    <dl>
      <dt id="event_delete"><code>"delete" ()</code></dt>
      <dd>Will be fired when the line object is deleted. A line object
      is associated with the <em>start</em> of the line. Mostly useful
      when you need to find out when your <a href="#setGutterMarker">gutter
      markers</a> on a given line are removed.</dd>
      <dt id="event_line_change"><code>"change" (line, changeObj)</code></dt>
      <dd>Fires when the line's text content is changed in any way
      (but the line is not deleted outright). The <code>change</code>
      object is similar to the one passed
      to <a href="#event_change">change event</a> on the editor
      object.</dd>
    </dl>

    <p>Marked range handles, as returned
    by <a href="#markText"><code>markText</code></a>
    and <a href="#setBookmark"><code>setBookmark</code></a>, emit the
    following events:</p>

    <dl>
      <dt id="event_beforeCursorEnter"><code>"beforeCursorEnter" ()</code></dt>
      <dd>Fired when the cursor enters the marked range. From this
      event handler, the editor state may be inspected
      but <em>not</em> modified, with the exception that the range on
      which the event fires may be cleared.</dd>
      <dt id="event_clear"><code>"clear" ()</code></dt>
      <dd>Fired when the range is cleared, either through cursor
      movement in combination
      with <a href="#mark_clearOnEnter"><code>clearOnEnter</code></a>
      or through a call to its <code>clear()</code> method. Will only
      be fired once per handle. Note that deleting the range through
      text editing does not fire this event, because an undo
      action might bring the range back into existence.</dd>
      <dt id="event_hide"><code>"hide" ()</code></dt>
      <dd>Fired when the last part of the marker is removed from the
      document by editing operations.</dd>
      <dt id="event_unhide"><code>"unhide" ()</code></dt>
      <dd>Fired when, after the marker was removed by editing, a undo
      operation brought the marker back.</dd>
    </dl>

    <p>Line widgets, returned
    by <a href="#addLineWidget"><code>addLineWidget</code></a>, fire
    these events:</p>

    <dl>
      <dt id="event_redraw"><code>"redraw" ()</code></dt>
      <dd>Fired whenever the editor re-adds the widget to the DOM.
      This will happen once right after the widget is added (if it is
      scrolled into view), and then again whenever it is scrolled out
      of view and back in again, or when changes to the editor options
      or the line the widget is on require the widget to be
      redrawn.</dd>
    </dl>

    <h2 id="keymaps">Keymaps</h2>

    <p>Keymaps are ways to associate keys with functionality. A keymap
    is an object mapping strings that identify the keys to functions
    that implement their functionality.</p>

    <p>Keys are identified either by name or by character.
    The <code>CodeMirror.keyNames</code> object defines names for
    common keys and associates them with their key codes. Examples of
    names defined here are <code>Enter</code>, <code>F5</code>,
    and <code>Q</code>. These can be prefixed
    with <code>Shift-</code>, <code>Cmd-</code>, <code>Ctrl-</code>,
    and <code>Alt-</code> (in that order!) to specify a modifier. So
    for example, <code>Shift-Ctrl-Space</code> would be a valid key
    identifier.</p>

    <p>Common example: map the Tab key to insert spaces instead of a tab
    character.</p>

    <pre data-lang="javascript">
{
  Tab: function(cm) {
    var spaces = Array(cm.getOption("indentUnit") + 1).join(" ");
    cm.replaceSelection(spaces, "end", "+input");
  }
}</pre>

    <p>Alternatively, a character can be specified directly by
    surrounding it in single quotes, for example <code>'$'</code>
    or <code>'q'</code>. Due to limitations in the way browsers fire
    key events, these may not be prefixed with modifiers.</p>

    <p>The <code>CodeMirror.keyMap</code> object associates keymaps
    with names. User code and keymap definitions can assign extra
    properties to this object. Anywhere where a keymap is expected, a
    string can be given, which will be looked up in this object. It
    also contains the <code>"default"</code> keymap holding the
    default bindings.</p>

    <p id="commands">The values of properties in keymaps can be either functions of
    a single argument (the CodeMirror instance), strings, or
    <code>false</code>. Such strings refer to properties of the
    <code>CodeMirror.commands</code> object, which defines a number of
    common commands that are used by the default keybindings, and maps
    them to functions. If the property is set to <code>false</code>,
    CodeMirror leaves handling of the key up to the browser. A key
    handler function may return <code>CodeMirror.Pass</code> to indicate
    that it has decided not to handle the key, and other handlers (or
    the default behavior) should be given a turn.</p>

    <p>Keys mapped to command names that start with the
    characters <code>"go"</code> (which should be used for
    cursor-movement actions) will be fired even when an
    extra <code>Shift</code> modifier is present (i.e. <code>"Up":
    "goLineUp"</code> matches both up and shift-up). This is used to
    easily implement shift-selection.</p>

    <p>Keymaps can defer to each other by defining
    a <code>fallthrough</code> property. This indicates that when a
    key is not found in the map itself, one or more other maps should
    be searched. It can hold either a single keymap or an array of
    keymaps.</p>

    <p>When a keymap contains a <code>nofallthrough</code> property
    set to <code>true</code>, keys matched against that map will be
    ignored if they don't match any of the bindings in the map (no
    further child maps will be tried, and the default effect of
    inserting a character will not occur).</p>

    <h2 id="styling">Customized Styling</h2>

    <p>Up to a certain extent, CodeMirror's look can be changed by
    modifying style sheet files. The style sheets supplied by modes
    simply provide the colors for that mode, and can be adapted in a
    very straightforward way. To style the editor itself, it is
    possible to alter or override the styles defined
    in <a href="../lib/codemirror.css"><code>codemirror.css</code></a>.</p>

    <p>Some care must be taken there, since a lot of the rules in this
    file are necessary to have CodeMirror function properly. Adjusting
    colors should be safe, of course, and with some care a lot of
    other things can be changed as well. The CSS classes defined in
    this file serve the following roles:</p>

    <dl>
      <dt id="class_CodeMirror"><code>CodeMirror</code></dt>
      <dd>The outer element of the editor. This should be used for the
      editor width, height, borders and positioning. Can also be used
      to set styles that should hold for everything inside the editor
      (such as font and font size), or to set a background.</dd>

      <dt id="class_CodeMirror_scroll"><code>CodeMirror-scroll</code></dt>
      <dd>Whether the editor scrolls (<code>overflow: auto</code> +
      fixed height). By default, it does. Setting
      the <code>CodeMirror</code> class to have <code>height:
      auto</code> and giving this class <code>overflow-x: auto;
      overflow-y: hidden;</code> will cause the editor
      to <a href="../demo/resize.html">resize to fit its
      content</a>.</dd>

      <dt id="class_CodeMirror_focused"><code>CodeMirror-focused</code></dt>
      <dd>Whenever the editor is focused, the top element gets this
      class. This is used to hide the cursor and give the selection a
      different color when the editor is not focused.</dd>

      <dt id="class_CodeMirror_gutters"><code>CodeMirror-gutters</code></dt>
      <dd>This is the backdrop for all gutters. Use it to set the
      default gutter background color, and optionally add a border on
      the right of the gutters.</dd>

      <dt id="class_CodeMirror_linenumbers"><code>CodeMirror-linenumbers</code></dt>
      <dd>Use this for giving a background or width to the line number
      gutter.</dd>

      <dt id="class_CodeMirror_linenumber"><code>CodeMirror-linenumber</code></dt>
      <dd>Used to style the actual individual line numbers. These
      won't be children of the <code>CodeMirror-linenumbers</code>
      (plural) element, but rather will be absolutely positioned to
      overlay it. Use this to set alignment and text properties for
      the line numbers.</dd>

      <dt id="class_CodeMirror_lines"><code>CodeMirror-lines</code></dt>
      <dd>The visible lines. This is where you specify vertical
      padding for the editor content.</dd>

      <dt id="class_CodeMirror_cursor"><code>CodeMirror-cursor</code></dt>
      <dd>The cursor is a block element that is absolutely positioned.
      You can make it look whichever way you want.</dd>

      <dt id="class_CodeMirror_selected"><code>CodeMirror-selected</code></dt>
      <dd>The selection is represented by <code>span</code> elements
      with this class.</dd>

      <dt id="class_CodeMirror_matchingbracket"><code>CodeMirror-matchingbracket</code>,
        <code>CodeMirror-nonmatchingbracket</code></dt>
      <dd>These are used to style matched (or unmatched) brackets.</dd>
    </dl>

    <p>If your page's style sheets do funky things to
    all <code>div</code> or <code>pre</code> elements (you probably
    shouldn't do that), you'll have to define rules to cancel these
    effects out again for elements under the <code>CodeMirror</code>
    class.</p>

    <p>Themes are also simply CSS files, which define colors for
    various syntactic elements. See the files in
    the <a href="../theme/"><code>theme</code></a> directory.</p>

    <h2 id="api">Programming API</h2>

    <p>A lot of CodeMirror features are only available through its
    API. Thus, you need to write code (or
    use <a href="#addons">add-ons</a>) if you want to expose them to
    your users.</p>

    <p>Whenever points in the document are represented, the API uses
    objects with <code>line</code> and <code>ch</code> properties.
    Both are zero-based. CodeMirror makes sure to 'clip' any positions
    passed by client code so that they fit inside the document, so you
    shouldn't worry too much about sanitizing your coordinates. If you
    give <code>ch</code> a value of <code>null</code>, or don't
    specify it, it will be replaced with the length of the specified
    line.</p>

    <p>Methods prefixed with <code>doc.</code> can, unless otherwise
    specified, be called both on <code>CodeMirror</code> (editor)
    instances and <code>CodeMirror.Doc</code> instances. Methods
    prefixed with <code>cm.</code> are <em>only</em> available
    on <code>CodeMirror</code> instances.</p>

    <h3 id="api_content">Content manipulation methods</h3>

    <dl>
      <dt id="getValue"><code>doc.getValue() → string</code></dt>
      <dd>Get the current editor content. You can pass it an optional
      argument to specify the string to be used to separate lines
      (defaults to <code>"\n"</code>).</dd>
      <dt id="setValue"><code>doc.setValue(string)</code></dt>
      <dd>Set the editor content.</dd>

      <dt id="getRange"><code>doc.getRange(from, to) → string</code></dt>
      <dd>Get the text between the given points in the editor, which
      should be <code>{line, ch}</code> objects. An optional third
      argument can be given to indicate the line separator string to
      use (defaults to <code>"\n"</code>).</dd>
      <dt id="replaceRange"><code>doc.replaceRange(string, from, to)</code></dt>
      <dd>Replace the part of the document between <code>from</code>
      and <code>to</code> with the given string. <code>from</code>
      and <code>to</code> must be <code>{line, ch}</code>
      objects. <code>to</code> can be left off to simply insert the
      string at position <code>from</code>.</dd>

      <dt id="getLine"><code>doc.getLine(n) → string</code></dt>
      <dd>Get the content of line <code>n</code>.</dd>
      <dt id="setLine"><code>doc.setLine(n, text)</code></dt>
      <dd>Set the content of line <code>n</code>.</dd>
      <dt id="removeLine"><code>doc.removeLine(n)</code></dt>
      <dd>Remove the given line from the document.</dd>

      <dt id="lineCount"><code>doc.lineCount() → number</code></dt>
      <dd>Get the number of lines in the editor.</dd>
      <dt id="firstLine"><code>doc.firstLine() → number</code></dt>
      <dt id="lastLine"><code>doc.lastLine() → number</code></dt>
      <dd>Get the first and last lines of the editor. This will
      usually be zero and <code>doc.lineCount() - 1</code> respectively,
      but for <a href="#linkedDoc_from">linked sub-views</a>,
      or <a href="#api_doc">documents</a> instantiated with a non-zero
      first line, it might return other values.</dd>

      <dt id="getLineHandle"><code>doc.getLineHandle(num) → lineHandle</code></dt>
      <dd>Fetches the line handle for the given line number.</dd>
      <dt id="getLineNumber"><code>doc.getLineNumber(handle) → integer</code></dt>
      <dd>Given a line handle, returns the current position of that
      line (or <code>null</code> when it is no longer in the
      document).</dd>
      <dt id="eachLine"><code>doc.eachLine(f) | doc.eachLine(start, end, f)</code></dt>
      <dd>Iterate over the whole document, or if <code>start</code>
      and <code>end</code> line numbers are given, the range
      from <code>start</code> up to (not including) <code>end</code>,
      and call <code>f</code> for each line, passing the line handle.
      This is a faster way to visit a range of line handlers than
      calling <a href="#getLineHandle"><code>getLineHandle</code></a>
      for each of them. Note that line handles have
      a <code>text</code> property containing the line's content (as a
      string).</dd>

      <dt id="markClean"><code>doc.markClean()</code></dt>
      <dd>Set the editor content as 'clean', a flag that it will
      retain until it is edited, and which will be set again when such
      an edit is undone again. Useful to track whether the content
      needs to be saved.</dd>
      <dt id="isClean"><code>doc.isClean() → boolean</code></dt>
      <dd>Returns whether the document is currently clean (not
      modified since initialization or the last call
      to <a href="#markClean"><code>markClean</code></a>).</dd>
    </dl>

    <h3 id="api_selection">Cursor and selection methods</h3>

    <dl>
      <dt id="getSelection"><code>doc.getSelection() → string</code></dt>
      <dd>Get the currently selected code.</dd>
      <dt id="replaceSelection"><code>doc.replaceSelection(string)</code></dt>
      <dd>Replace the selection with the given string.</dd>

      <dt id="getCursor"><code>doc.getCursor(start) → object</code></dt>
      <dd><code>start</code> is a an optional string indicating which
      end of the selection to return. It may
      be <code>"start"</code>, <code>"end"</code>, <code>"head"</code>
      (the side of the selection that moves when you press
      shift+arrow), or <code>"anchor"</code> (the fixed side of the
      selection). Omitting the argument is the same as
      passing <code>"head"</code>. A <code>{line, ch}</code> object
      will be returned.</dd>
      <dt id="somethingSelected"><code>doc.somethingSelected() → boolean</code></dt>
      <dd>Return true if any text is selected.</dd>
      <dt id="setCursor"><code>doc.setCursor(pos)</code></dt>
      <dd>Set the cursor position. You can either pass a
      single <code>{line, ch}</code> object, or the line and the
      character as two separate parameters.</dd>
      <dt id="setSelection"><code>doc.setSelection(anchor, head)</code></dt>
      <dd>Set the selection range. <code>anchor</code>
      and <code>head</code> should be <code>{line, ch}</code>
      objects. <code>head</code> defaults to <code>anchor</code> when
      not given.</dd>
      <dt id="extendSelection"><code>doc.extendSelection(pos, pos2)</code></dt>
      <dd>Similar
      to <a href="#setSelection"><code>setSelection</code></a>, but
      will, if shift is held or
      the <a href="#setExtending">extending</a> flag is set, move the
      head of the selection while leaving the anchor at its current
      place. <code>pos2</code> is optional, and can be passed to
      ensure a region (for example a word or paragraph) will end up
      selected (in addition to whatever lies between that region and
      the current anchor).</dd>
      <dt id="setExtending"><code>doc.setExtending(bool)</code></dt>
      <dd>Sets or clears the 'extending' flag, which acts similar to
      the shift key, in that it will cause cursor movement and calls
      to <a href="#extendSelection"><code>extendSelection</code></a>
      to leave the selection anchor in place.</dd>

      <dt id="hasFocus"><code>cm.hasFocus() → bool</code></dt>
      <dd>Tells you whether the editor currently has focus.</dd>

      <dt id="findPosH"><code>cm.findPosH(start, amount, unit, visually) → object</code></dt>
      <dd>Used to find the target position for horizontal cursor
      motion. <code>start</code> is a <code>{line, ch}</code>
      object, <code>amount</code> an integer (may be negative),
      and <code>unit</code> one of the
      string <code>"char"</code>, <code>"column"</code>,
      or <code>"word"</code>. Will return a position that is produced
      by moving <code>amount</code> times the distance specified
      by <code>unit</code>. When <code>visually</code> is true, motion
      in right-to-left text will be visual rather than logical. When
      the motion was clipped by hitting the end or start of the
      document, the returned value will have a <code>hitSide</code>
      property set to true.</dd>
      <dt id="findPosV"><code>cm.findPosV(start, amount, unit) → object</code></dt>
      <dd>Similar to <a href="#findPosH"><code>findPosH</code></a>,
      but used for vertical motion. <code>unit</code> may
      be <code>"line"</code> or <code>"page"</code>. The other
      arguments and the returned value have the same interpretation as
      they have in <code>findPosH</code>.</dd>
    </dl>

    <h3 id="api_configuration">Configuration methods</h3>

    <dl>
      <dt id="setOption"><code>cm.setOption(option, value)</code></dt>
      <dd>Change the configuration of the editor. <code>option</code>
      should the name of an <a href="#config">option</a>,
      and <code>value</code> should be a valid value for that
      option.</dd>
      <dt id="getOption"><code>cm.getOption(option) → value</code></dt>
      <dd>Retrieves the current value of the given option for this
      editor instance.</dd>

      <dt id="addKeyMap"><code>cm.addKeyMap(map, bottom)</code></dt>
      <dd>Attach an additional <a href="#keymaps">keymap</a> to the
      editor. This is mostly useful for add-ons that need to register
      some key handlers without trampling on
      the <a href="#option_extraKeys"><code>extraKeys</code></a>
      option. Maps added in this way have a higher precedence than
      the <code>extraKeys</code>
      and <a href="#option_keyMap"><code>keyMap</code></a> options,
      and between them, the maps added earlier have a lower precedence
      than those added later, unless the <code>bottom</code> argument
      was passed, in which case they end up below other keymaps added
      with this method.</dd>
      <dt id="removeKeyMap"><code>cm.removeKeyMap(map)</code></dt>
      <dd>Disable a keymap added
      with <a href="#addKeyMap"><code>addKeyMap</code></a>. Either
      pass in the keymap object itself, or a string, which will be
      compared against the <code>name</code> property of the active
      keymaps.</dd>

      <dt id="addOverlay"><code>cm.addOverlay(mode, options)</code></dt>
      <dd>Enable a highlighting overlay. This is a stateless mini-mode
      that can be used to add extra highlighting. For example,
      the <a href="../demo/search.html">search add-on</a> uses it to
      highlight the term that's currently being
      searched. <code>mode</code> can be a <a href="#option_mode">mode
      spec</a> or a mode object (an object with
      a <a href="#token"><code>token</code></a> method).
      The <code>options</code> parameter is optional. If given, it
      should be an object. Currently, only the <code>opaque</code>
      option is recognized. This defaults to off, but can be given to
      allow the overlay styling, when not <code>null</code>, to
      override the styling of the base mode entirely, instead of the
      two being applied together.</dd>
      <dt id="removeOverlay"><code>cm.removeOverlay(mode)</code></dt>
      <dd>Pass this the exact argument passed for
      the <code>mode</code> parameter
      to <a href="#addOverlay"><code>addOverlay</code></a> to remove
      an overlay again.</dd>

      <dt id="on"><code>cm.on(type, func)</code></dt>
      <dd>Register an event handler for the given event type (a
      string) on the editor instance. There is also
      a <code>CodeMirror.on(object, type, func)</code> version
      that allows registering of events on any object.</dd>
      <dt id="off"><code>cm.off(type, func)</code></dt>
      <dd>Remove an event handler on the editor instance. An
      equivalent <code>CodeMirror.off(object, type,
      func)</code> also exists.</dd>
    </dl>

    <h3 id="api_doc">Document management methods</h3>

    <p id="Doc">Each editor is associated with an instance
    of <code>CodeMirror.Doc</code>, its document. A document
    represents the editor content, plus a selection, an undo history,
    and a <a href="#option_mode">mode</a>. A document can only be
    associated with a single editor at a time. You can create new
    documents by calling the <code>CodeMirror.Doc(text, mode,
    firstLineNumber)</code> constructor. The last two arguments are
    optional and can be used to set a mode for the document and make
    it start at a line number other than 0, respectively.</p>

    <dl>
      <dt id="getDoc"><code>cm.getDoc() → doc</code></dt>
      <dd>Retrieve the currently active document from an editor.</dd>
      <dt id="getEditor"><code>doc.getEditor() → editor</code></dt>
      <dd>Retrieve the editor associated with a document. May
      return <code>null</code>.</dd>

      <dt id="swapDoc"><code>cm.swapDoc(doc) → doc</code></dt>
      <dd>Attach a new document to the editor. Returns the old
      document, which is now no longer associated with an editor.</dd>

      <dt id="copy"><code>doc.copy(copyHistory) → doc</code></dt>
      <dd>Create an identical copy of the given doc.
      When <code>copyHistory</code> is true, the history will also be
      copied. Can not be called directly on an editor.</dd>

      <dt id="linkedDoc"><code>doc.linkedDoc(options) → doc</code></dt>
      <dd>Create a new document that's linked to the target document.
      Linked documents will stay in sync (changes to one are also
      applied to the other) until <a href="#unlinkDoc">unlinked</a>.
      These are the options that are supported:
        <dl>
          <dt id="linkedDoc_sharedHist"><code>sharedHist (boolean)</code></dt>
          <dd>When turned on, the linked copy will share an undo
          history with the original. Thus, something done in one of
          the two can be undone in the other, and vice versa.</dd>
          <dt id="linkedDoc_from"><code>from, to (integer)</code></dt>
          <dd>Can be given to make the new document a subview of the
          original. Subviews only show a given range of lines. Note
          that line coordinates inside the subview will be consistent
          with those of the parent, so that for example a subview
          starting at line 10 will refer to its first line as line 10,
          not 0.</dd>
          <dt id="linkedDoc_mode"><code>mode (mode spec)</code></dt>
          <dd>By default, the new document inherits the mode of the
          parent. This option can be set to
          a <a href="#option_mode">mode spec</a> to give it a
          different mode.</dd>
        </dl></dd>
      <dt id="unlinkDoc"><code>doc.unlinkDoc(doc)</code></dt>
      <dd>Break the link between two documents. After calling this,
      changes will no longer propagate between the documents, and, if
      they had a shared history, the history will become
      separate.</dd>
      <dt id="iterLinkedDocs"><code>doc.iterLinkedDocs(function)</code></dt>
      <dd>Will call the given function for all documents linked to the
      target document. It will be passed two arguments, the linked document
      and a boolean indicating whether that document shares history
      with the target.</dd>
    </dl>

    <h3 id="api_history">History-related methods</h3>

    <dl>
      <dt id="undo"><code>doc.undo()</code></dt>
      <dd>Undo one edit (if any undo events are stored).</dd>
      <dt id="redo"><code>doc.redo()</code></dt>
      <dd>Redo one undone edit.</dd>

      <dt id="historySize"><code>doc.historySize() → object</code></dt>
      <dd>Returns an object with <code>{undo, redo}</code> properties,
      both of which hold integers, indicating the amount of stored
      undo and redo operations.</dd>
      <dt id="clearHistory"><code>doc.clearHistory()</code></dt>
      <dd>Clears the editor's undo history.</dd>
      <dt id="getHistory"><code>doc.getHistory() → object</code></dt>
      <dd>Get a (JSON-serializeable) representation of the undo history.</dd>
      <dt id="setHistory"><code>doc.setHistory(object)</code></dt>
      <dd>Replace the editor's undo history with the one provided,
      which must be a value as returned
      by <a href="#getHistory"><code>getHistory</code></a>. Note that
      this will have entirely undefined results if the editor content
      isn't also the same as it was when <code>getHistory</code> was
      called.</dd>
    </dl>

    <h3 id="api_marker">Text-marking methods</h3>

    <dl>
      <dt id="markText"><code>doc.markText(from, to, options) → object</code></dt>
      <dd>Can be used to mark a range of text with a specific CSS
      class name. <code>from</code> and <code>to</code> should
      be <code>{line, ch}</code> objects. The <code>options</code>
      parameter is optional. When given, it should be an object that
      may contain the following configuration options:
      <dl>
        <dt id="mark_className"><code>className (string)</code></dt>
        <dd>Assigns a CSS class to the marked stretch of text.</dd>
        <dt id="mark_inclusiveLeft"><code>inclusiveLeft (boolean)</code></dt><dd>Determines whether
        text inserted on the left of the marker will end up inside
        or outside of it.</dd>
        <dt id="mark_inclusiveRight"><code>inclusiveRight</code> (boolean)</dt><dd>Like <code>inclusiveLeft</code>,
        but for the right side.</dd>
        <dt id="mark_atomic"><code>atomic (boolean)</code></dt>
        <dd>Atomic ranges act as a single unit when cursor movement is
        concerned—i.e. it is impossible to place the cursor inside of
        them. In atomic ranges, <code>inclusiveLeft</code>
        and <code>inclusiveRight</code> have a different meaning—they
        will prevent the cursor from being placed respectively
        directly before and directly after the range.</dd>
        <dt id="mark_collapsed"><code>collapsed (boolean)</code></dt>
        <dd>Collapsed ranges do not show up in the display. Setting a
        range to be collapsed will automatically make it atomic.</dd>
        <dt id="mark_clearOnEnter"><code>clearOnEnter (boolean)</code></dt>
        <dd>When enabled, will cause the mark to clear itself whenever
        the cursor enters its range. This is mostly useful for
        text-replacement widgets that need to 'snap open' when the
        user tries to edit them. A
        the <a href="#event_clear"><code>"clear"</code></a> event
        fired on the range handle can be used to be notified when this
        happens.</dd>
        <dt id="mark_replacedWith"><code>replacedWith (dom node)</code></dt>
        <dd>Use a given node to display this range. Implies both
        collapsed and atomic. The given DOM node <em>must</em> be an
        inline element (as opposed to a block element).</dd>
        <dt id="mark_readOnly"><code>readOnly</code></dt>
        <dd>A read-only span can, as long as it is not cleared, not be
        modified except by
        calling <a href="#setValue"><code>setValue</code></a> to reset
        the whole document. <em>Note:</em> adding a read-only span
        currently clears the undo history of the editor, because
        existing undo events being partially nullified by read-only
        spans would corrupt the history (in the current
        implementation).</dd>
        <dt id="mark_startStyle"><code>startStyle</code></dt><dd>Can be used to specify
        an extra CSS class to be applied to the leftmost span that
        is part of the marker.</dd>
        <dt id="mark_endStyle"><code>endStyle</code></dt><dd>Equivalent
        to <code>startStyle</code>, but for the rightmost span.</dd>
        <dt id="mark_shared"><code>shared</code></dt><dd>When the
        target document is <a href="#linkedDoc">linked</a> to other
        documents, you can set <code>shared</code> to true to make the
        marker appear in all documents. By default, a marker appears
        only in its target document.</dd>
      </dl>
      The method will return an object that represents the marker
      (with constuctor <code>CodeMirror.TextMarker</code>), which
      exposes three methods:
      <code>clear()</code>, to remove the mark,
      <code>find()</code>, which returns a <code>{from, to}</code>
      object (both holding document positions), indicating the current
      position of the marked range, or <code>undefined</code> if the
      marker is no longer in the document, and
      finally <code>getOptions(copyWidget)</code>, which returns an
      object representing the options for the marker.
      If <code>copyWidget</code> is given an true, it will clone the
      value of
      the <a href="#mark_replacedWith"><code>replacedWith</code></a>
      option, if any.</dd>

      <dt id="setBookmark"><code>doc.setBookmark(pos, options) → object</code></dt>
      <dd>Inserts a bookmark, a handle that follows the text around it
      as it is being edited, at the given position. A bookmark has two
      methods <code>find()</code> and <code>clear()</code>. The first
      returns the current position of the bookmark, if it is still in
      the document, and the second explicitly removes the bookmark.
      The options argument is optional. If given, the following
      properties are recognized:
      <dl>
        <dt><code>widget</code></dt><dd>Can be used to display a DOM
        node at the current location of the bookmark (analogous to
        the <a href="#mark_replacedWith"><code>replacedWith</code></a>
        option to <code>markText</code>).</dd>
        <dt><code>insertLeft</code></dt><dd>By default, text typed
        when the cursor is on top of the bookmark will end up to the
        right of the bookmark. Set this option to true to make it go
        to the left instead.</dd>
      </dl></dd>

      <dt id="findMarksAt"><code>doc.findMarksAt(pos) → array</code></dt>
      <dd>Returns an array of all the bookmarks and marked ranges
      present at the given position.</dd>
      <dt id="getAllMarks"><code>doc.getAllMarks() → array</code></dt>
      <dd>Returns an array containing all marked ranges in the document.</dd>
    </dl>

    <h3 id="api_decoration">Widget, gutter, and decoration methods</h3>
    
    <dl>
      <dt id="setGutterMarker"><code>cm.setGutterMarker(line, gutterID, value) → lineHandle</code></dt>
      <dd>Sets the gutter marker for the given gutter (identified by
      its CSS class, see
      the <a href="#option_gutters"><code>gutters</code></a> option)
      to the given value. Value can be either <code>null</code>, to
      clear the marker, or a DOM element, to set it. The DOM element
      will be shown in the specified gutter next to the specified
      line.</dd>
      
      <dt id="clearGutter"><code>cm.clearGutter(gutterID)</code></dt>
      <dd>Remove all gutter markers in
      the <a href="#option_gutters">gutter</a> with the given ID.</dd>

      <dt id="addLineClass"><code>cm.addLineClass(line, where, class) → lineHandle</code></dt>
      <dd>Set a CSS class name for the given line. <code>line</code>
      can be a number or a line handle. <code>where</code> determines
      to which element this class should be applied, can can be one
      of <code>"text"</code> (the text element, which lies in front of
      the selection), <code>"background"</code> (a background element
      that will be behind the selection), or <code>"wrap"</code> (the
      wrapper node that wraps all of the line's elements, including
      gutter elements). <code>class</code> should be the name of the
      class to apply.</dd>

      <dt id="removeLineClass"><code>cm.removeLineClass(line, where, class) → lineHandle</code></dt>
      <dd>Remove a CSS class from a line. <code>line</code> can be a
      line handle or number. <code>where</code> should be one
      of <code>"text"</code>, <code>"background"</code>,
      or <code>"wrap"</code>
      (see <a href="#addLineClass"><code>addLineClass</code></a>). <code>class</code>
      can be left off to remove all classes for the specified node, or
      be a string to remove only a specific class.</dd>

      <dt id="lineInfo"><code>cm.lineInfo(line) → object</code></dt>
      <dd>Returns the line number, text content, and marker status of
      the given line, which can be either a number or a line handle.
      The returned object has the structure <code>{line, handle, text,
      gutterMarkers, textClass, bgClass, wrapClass, widgets}</code>,
      where <code>gutterMarkers</code> is an object mapping gutter IDs
      to marker elements, and <code>widgets</code> is an array
      of <a href="#addLineWidget">line widgets</a> attached to this
      line, and the various class properties refer to classes added
      with <a href="#addLineClass"><code>addLineClass</code></a>.</dd>

      <dt id="addWidget"><code>cm.addWidget(pos, node, scrollIntoView)</code></dt>
      <dd>Puts <code>node</code>, which should be an absolutely
      positioned DOM node, into the editor, positioned right below the
      given <code>{line, ch}</code> position.
      When <code>scrollIntoView</code> is true, the editor will ensure
      that the entire node is visible (if possible). To remove the
      widget again, simply use DOM methods (move it somewhere else, or
      call <code>removeChild</code> on its parent).</dd>

      <dt id="addLineWidget"><code>cm.addLineWidget(line, node, options) → object</code></dt>
      <dd>Adds a line widget, an element shown below a line, spanning
      the whole of the editor's width, and moving the lines below it
      downwards. <code>line</code> should be either an integer or a
      line handle, and <code>node</code> should be a DOM node, which
      will be displayed below the given line. <code>options</code>,
      when given, should be an object that configures the behavior of
      the widget. The following options are supported (all default to
      false):
        <dl>
          <dt><code>coverGutter (boolean)</code></dt>
          <dd>Whether the widget should cover the gutter.</dd>
          <dt><code>noHScroll (boolean)</code></dt>
          <dd>Whether the widget should stay fixed in the face of
          horizontal scrolling.</dd>
          <dt><code>above (boolean)</code></dt>
          <dd>Causes the widget to be placed above instead of below
          the text of the line.</dd>
          <dt><code>showIfHidden (boolean)</code></dt>
          <dd>When true, will cause the widget to be rendered even if
          the line it is associated with is hidden.</dd>
        </dl>
      Note that the widget node will become a descendant of nodes with
      CodeMirror-specific CSS classes, and those classes might in some
      cases affect it. This method returns an object that represents
      the widget placement. It'll have a <code>line</code> property
      pointing at the line handle that it is associated with, and the following methods:
        <dl>
          <dt id="widget_clear"><code>clear()</code></dt><dd>Removes the widget.</dd>
          <dt id="widget_changed"><code>changed()</code></dt><dd>Call
          this if you made some change to the widget's DOM node that
          might affect its height. It'll force CodeMirror to update
          the height of the line that contains the widget.</dd>
        </dl>
      </dd>

    <h3 id="api_sizing">Sizing, scrolling and positioning methods</h3>

    <dl>
      <dt id="setSize"><code>cm.setSize(width, height)</code></dt>
      <dd>Programatically set the size of the editor (overriding the
      applicable <a href="#css-resize">CSS
      rules</a>). <code>width</code> and <code>height</code> height
      can be either numbers (interpreted as pixels) or CSS units
      (<code>"100%"</code>, for example). You can
      pass <code>null</code> for either of them to indicate that that
      dimension should not be changed.</dd>

      <dt id="scrollTo"><code>cm.scrollTo(x, y)</code></dt>
      <dd>Scroll the editor to a given (pixel) position. Both
      arguments may be left as <code>null</code>
      or <code>undefined</code> to have no effect.</dd>
      <dt id="getScrollInfo"><code>cm.getScrollInfo()</code></dt>
      <dd>Get an <code>{left, top, width, height, clientWidth,
      clientHeight}</code> object that represents the current scroll
      position, the size of the scrollable area, and the size of the
      visible area (minus scrollbars).</dd>
      <dt id="scrollIntoView"><code>cm.scrollIntoView(pos, margin)</code></dt>
      <dd>Scrolls the given element into view. <code>pos</code> may be
      either a <code>{line, ch}</code> position, referring to a given
      character, <code>null</code>, to refer to the cursor, or
      a <code>{left, top, right, bottom}</code> object, in
      editor-local coordinates. The <code>margin</code> parameter is
      optional. When given, it indicates the amount of pixels around
      the given area that should be made visible as well.</dd>

      <dt id="cursorCoords"><code>cm.cursorCoords(where, mode) → object</code></dt>
      <dd>Returns an <code>{left, top, bottom}</code> object
      containing the coordinates of the cursor position.
      If <code>mode</code> is <code>"local"</code>, they will be
      relative to the top-left corner of the editable document. If it
      is <code>"page"</code> or not given, they are relative to the
      top-left corner of the page. <code>where</code> can be a boolean
      indicating whether you want the start (<code>true</code>) or the
      end (<code>false</code>) of the selection, or, if a <code>{line,
      ch}</code> object is given, it specifies the precise position at
      which you want to measure.</dd>
      <dt id="charCoords"><code>cm.charCoords(pos, mode) → object</code></dt>
      <dd>Returns the position and dimensions of an arbitrary
      character. <code>pos</code> should be a <code>{line, ch}</code>
      object. This differs from <code>cursorCoords</code> in that
      it'll give the size of the whole character, rather than just the
      position that the cursor would have when it would sit at that
      position.</dd>
      <dt id="coordsChar"><code>cm.coordsChar(object, mode) → pos</code></dt>
      <dd>Given an <code>{left, top}</code> object, returns
      the <code>{line, ch}</code> position that corresponds to it. The
      optional <code>mode</code> parameter determines relative to what
      the coordinates are interpreted. It may
      be <code>"window"</code>, <code>"page"</code> (the default),
      or <code>"local"</code>.</dd>
      <dt id="defaultTextHeight"><code>cm.defaultTextHeight() → number</code></dt>
      <dd>Returns the line height of the default font for the editor.</dd>
      <dt id="defaultCharWidth"><code>cm.defaultCharWidth() → number</code></dt>
      <dd>Returns the pixel width of an 'x' in the default font for
      the editor. (Note that for non-monospace fonts, this is mostly
      useless, and even for monospace fonts, non-ascii characters
      might have a different width).</dd>

      <dt id="getViewport"><code>cm.getViewport() → object</code></dt>
      <dd>Returns a <code>{from, to}</code> object indicating the
      start (inclusive) and end (exclusive) of the currently rendered
      part of the document. In big documents, when most content is
      scrolled out of view, CodeMirror will only render the visible
      part, and a margin around it. See also
      the <a href="#event_viewportChange"><code>viewportChange</code></a>
      event.</dd>

      <dt id="refresh"><code>cm.refresh()</code></dt>
      <dd>If your code does something to change the size of the editor
      element (window resizes are already listened for), or unhides
      it, you should probably follow up by calling this method to
      ensure CodeMirror is still looking as intended.</dd>
    </dl>

    <h3 id="api_mode">Mode, state, and token-related methods</h3>

    <p>When writing language-aware functionality, it can often be
    useful to hook into the knowledge that the CodeMirror language
    mode has. See <a href="#modeapi">the section on modes</a> for a
    more detailed description of how these work.</p>

    <dl>
      <dt id="getMode"><code>doc.getMode() → object</code></dt>
      <dd>Gets the mode object for the editor. Note that this is
      distinct from <code>getOption("mode")</code>, which gives you
      the mode specification, rather than the resolved, instantiated
      <a href="#defineMode">mode object</a>.</dd>

      <dt id="getTokenAt"><code>cm.getTokenAt(pos) → object</code></dt>
      <dd>Retrieves information about the token the current mode found
      before the given position (a <code>{line, ch}</code> object). The
      returned object has the following properties:
      <dl>
        <dt><code>start</code></dt><dd>The character (on the given line) at which the token starts.</dd>
        <dt><code>end</code></dt><dd>The character at which the token ends.</dd>
        <dt><code>string</code></dt><dd>The token's string.</dd>
        <dt><code>type</code></dt><dd>The token type the mode assigned
        to the token, such as <code>"keyword"</code>
        or <code>"comment"</code> (may also be null).</dd>
        <dt><code>state</code></dt><dd>The mode's state at the end of this token.</dd>
      </dl></dd>

      <dt id="getStateAfter"><code>cm.getStateAfter(line) → state</code></dt>
      <dd>Returns the mode's parser state, if any, at the end of the
      given line number. If no line number is given, the state at the
      end of the document is returned. This can be useful for storing
      parsing errors in the state, or getting other kinds of
      contextual information for a line.</dd>
    </dl>

    <h3 id="api_misc">Miscellaneous methods</h3>

    <dl>
      <dt id="operation"><code>cm.operation(func) → result</code></dt>
      <dd>CodeMirror internally buffers changes and only updates its
      DOM structure after it has finished performing some operation.
      If you need to perform a lot of operations on a CodeMirror
      instance, you can call this method with a function argument. It
      will call the function, buffering up all changes, and only doing
      the expensive update after the function returns. This can be a
      lot faster. The return value from this method will be the return
      value of your function.</dd>

      <dt id="indentLine"><code>cm.indentLine(line, dir)</code></dt>
      <dd>Adjust the indentation of the given line. The second
      argument (which defaults to <code>"smart"</code>) may be one of:
        <dl>
          <dt><code>"prev"</code></dt>
          <dd>Base indentation on the indentation of the previous line.</dd>
          <dt><code>"smart"</code></dt>
          <dd>Use the mode's smart indentation if available, behave
          like <code>"prev"</code> otherwise.</dd>
          <dt><code>"add"</code></dt>
          <dd>Increase the indentation of the line by
          one <a href="#option_indentUnit">indent unit</a>.</dd>
          <dt><code>"subtract"</code></dt>
          <dd>Reduce the indentation of the line.</dd>
        </dl></dd>

      <dt id="posFromIndex"><code>doc.posFromIndex(index) → object</code></dt>
      <dd>Calculates and returns a <code>{line, ch}</code> object for a
      zero-based <code>index</code> who's value is relative to the start of the
      editor's text. If the <code>index</code> is out of range of the text then
      the returned object is clipped to start or end of the text
      respectively.</dd>
      <dt id="indexFromPos"><code>doc.indexFromPos(object) → number</code></dt>
      <dd>The reverse of <a href="#posFromIndex"><code>posFromIndex</code></a>.</dd>

      <dt id="focus"><code>cm.focus()</code></dt>
      <dd>Give the editor focus.</dd>

      <dt id="getInputField"><code>cm.getInputField() → textarea</code></dt>
      <dd>Returns the hidden textarea used to read input.</dd>
      <dt id="getWrapperElement"><code>cm.getWrapperElement() → node</code></dt>
      <dd>Returns the DOM node that represents the editor, and
      controls its size. Remove this from your tree to delete an
      editor instance.</dd>
      <dt id="getScrollerElement"><code>cm.getScrollerElement() → node</code></dt>
      <dd>Returns the DOM node that is responsible for the scrolling
      of the editor.</dd>
      <dt id="getGutterElement"><code>cm.getGutterElement() → node</code></dt>
      <dd>Fetches the DOM node that contains the editor gutters.</dd>
    </dl>

    <h3 id="api_static">Static properties</h3>

    <p id="version">The <code>CodeMirror</code> object itself provides
    several useful properties. Firstly, its <code>version</code>
    property contains a string that indicates the version of the
    library. For releases, this simply
    contains <code>"major.minor"</code> (for
    example <code>"2.33"</code>. For beta versions, <code>" B"</code>
    (space, capital B) is added at the end of the string, for
    development snapshots, <code>" +"</code> (space, plus) is
    added.</p>

    <p id="fromTextArea">The <code>CodeMirror.fromTextArea</code>
    method provides another way to initialize an editor. It takes a
    textarea DOM node as first argument and an optional configuration
    object as second. It will replace the textarea with a CodeMirror
    instance, and wire up the form of that textarea (if any) to make
    sure the editor contents are put into the textarea when the form
    is submitted. A CodeMirror instance created this way has three
    additional methods:</p>

    <dl>
      <dt id="save"><code>cm.save()</code></dt>
      <dd>Copy the content of the editor into the textarea.</dd>

      <dt id="toTextArea"><code>cm.toTextArea()</code></dt>
      <dd>Remove the editor, and restore the original textarea (with
      the editor's current content).</dd>

      <dt id="getTextArea"><code>cm.getTextArea() → textarea</code></dt>
      <dd>Returns the textarea that the instance was based on.</dd>
    </dl>

    <p id="defineExtension">If you want to define extra methods in terms
    of the CodeMirror API, it is possible to
    use <code>CodeMirror.defineExtension(name, value)</code>. This
    will cause the given value (usually a method) to be added to all
    CodeMirror instances created from then on.</p>

    <p id="defineOption">Similarly, <code>CodeMirror.defineOption(name,
    default, updateFunc)</code> can be used to define new options for
    CodeMirror. The <code>updateFunc</code> will be called with the
    editor instance and the new value when an editor is initialized,
    and whenever the option is modified
    through <a href="#setOption"><code>setOption</code></a>.</p>

    <p id="defineInitHook">If your extention just needs to run some
    code whenever a CodeMirror instance is initialized,
    use <code>CodeMirror.defineInitHook</code>. Give it a function as
    its only argument, and from then on, that function will be called
    (with the instance as argument) whenever a new CodeMirror instance
    is initialized.</p>

    <h2 id="addons">Add-ons</h2>

    <p>The <code>addon</code> directory in the distribution contains a
    number of reusable components that implement extra editor
    functionality. In brief, they are:</p>

    <dl>
      <dt id="addon_dialog"><a href="../addon/dialog/dialog.js"><code>dialog/dialog.js</code></a></dt>
      <dd>Provides a very simple way to query users for text input.
      Adds an <code>openDialog</code> method to CodeMirror instances,
      which can be called with an HTML fragment that provides the
      prompt (should include an <code>input</code> tag), and a
      callback function that is called when text has been entered.
      Depends on <code>addon/dialog/dialog.css</code>.</dd>
      <dt id="addon_searchcursor"><a href="../addon/search/searchcursor.js"><code>search/searchcursor.js</code></a></dt>
      <dd>Adds the <code>getSearchCursor(query, start, caseFold) →
      cursor</code> method to CodeMirror instances, which can be used
      to implement search/replace functionality. <code>query</code>
      can be a regular expression or a string (only strings will match
      across lines—if they contain newlines). <code>start</code>
      provides the starting position of the search. It can be
      a <code>{line, ch}</code> object, or can be left off to default
      to the start of the document. <code>caseFold</code> is only
      relevant when matching a string. It will cause the search to be
      case-insensitive. A search cursor has the following methods:
        <dl>
          <dt><code>findNext(), findPrevious() → boolean</code></dt>
          <dd>Search forward or backward from the current position.
          The return value indicates whether a match was found. If
          matching a regular expression, the return value will be the
          array returned by the <code>match</code> method, in case you
          want to extract matched groups.</dd>
          <dt><code>from(), to() → object</code></dt>
          <dd>These are only valid when the last call
          to <code>findNext</code> or <code>findPrevious</code> did
          not return false. They will return <code>{line, ch}</code>
          objects pointing at the start and end of the match.</dd>
          <dt><code>replace(text)</code></dt>
          <dd>Replaces the currently found match with the given text
          and adjusts the cursor position to reflect the
          replacement.</dd>
        </dl></dd>

      <dt id="addon_search"><a href="../addon/search/search.js"><code>search/search.js</code></a></dt>
      <dd>Implements the search commands. CodeMirror has keys bound to
      these by default, but will not do anything with them unless an
      implementation is provided. Depends
      on <code>searchcursor.js</code>, and will make use
      of <a href="#addon_dialog"><code>openDialog</code></a> when
      available to make prompting for search queries less ugly.</dd>
      <dt id="addon_matchbrackets"><a href="../addon/edit/matchbrackets.js"><code>edit/matchbrackets.js</code></a></dt>
      <dd>Defines an option <code>matchBrackets</code> which, when set
      to true, causes matching brackets to be highlighted whenever the
      cursor is next to them. It also adds a
      method <code>matchBrackets</code> that forces this to happen
      once, and a method <code>findMatchingBracket</code> that can be
      used to run the bracket-finding algorithm that this uses
      internally.</dd>
      <dt id="addon_closebrackets"><a href="../addon/edit/closebrackets.js"><code>edit/closebrackets.js</code></a></dt>
      <dd>Defines an option <code>autoCloseBrackets</code> that will
      auto-close brackets and quotes when typed. By default, it'll
      auto-close <code>()[]{}''""</code>, but you can pass it a
      string similar to that (containing pairs of matching characters)
      to customize it. <a href="../demo/closebrackets.html">Demo
      here</a>.</dd>
      <dt id="addon_foldcode"><a href="../addon/fold/foldcode.js"><code>fold/foldcode.js</code></a></dt>
      <dd>Helps with code folding.
      See <a href="../demo/folding.html">the demo</a> for an example.
      Call <code>CodeMirror.newFoldFunction</code> with a range-finder
      helper function to create a function that will, when applied to
      a CodeMirror instance and a line number, attempt to fold or
      unfold the block starting at the given line. A range-finder is a
      language-specific function that also takes an instance and a
      line number, and returns an range to be folded, or null if no
      block is started on that line. There are files in
      the <a href="../addon/fold/"><code>addon/fold/</code></a>
      directory providing <code>CodeMirror.braceRangeFinder</code>,
      which finds blocks in brace languages (JavaScript, C, Java,
      etc), <code>CodeMirror.indentRangeFinder</code>, for languages
      where indentation determines block structure (Python, Haskell),
      and <code>CodeMirror.tagRangeFinder</code>, for XML-style
      languages.</dd>
      <dt id="addon_runmode"><a href="../addon/runmode/runmode.js"><code>runmode/runmode.js</code></a></dt>
      <dd>Can be used to run a CodeMirror mode over text without
      actually opening an editor instance.
      See <a href="../demo/runmode.html">the demo</a> for an example.
      There are alternate versions of the file avaible for
      running <a href="../addon/runmode/runmode-standalone.js">stand-alone</a>
      (without including all of CodeMirror) and
      for <a href="../addon/runmode/runmode.node.js">running under
      node.js</a>.</dd>
      <dt id="addon_overlay"><a href="../addon/mode/overlay.js"><code>mode/overlay.js</code></a></dt>
      <dd>Mode combinator that can be used to extend a mode with an
      'overlay' — a secondary mode is run over the stream, along with
      the base mode, and can color specific pieces of text without
      interfering with the base mode.
      Defines <code>CodeMirror.overlayMode</code>, which is used to
      create such a mode. See <a href="../demo/mustache.html">this
      demo</a> for a detailed example.</dd>
      <dt id="addon_multiplex"><a href="../addon/mode/multiplex.js"><code>mode/multiplex.js</code></a></dt>
      <dd>Mode combinator that can be used to easily 'multiplex'
      between several modes.
      Defines <code>CodeMirror.multiplexingMode</code> which, when
      given as first argument a mode object, and as other arguments
      any number of <code>{open, close, mode [, delimStyle]}</code>
      objects, will return a mode object that starts parsing using the
      mode passed as first argument, but will switch to another mode
      as soon as it encounters a string that occurs in one of
      the <code>open</code> fields of the passed objects. When in a
      sub-mode, it will go back to the top mode again when
      the <code>close</code> string is encountered.
      Pass <code>"\n"</code> for <code>open</code> or <code>close</code>
      if you want to switch on a blank line.
      When <code>delimStyle</code> is specified, it will be the token
      style returned for the delimiter tokens. The outer mode will not
      see the content between the delimiters.
      See <a href="../demo/multiplex.html">this demo</a> for an
      example.</dd>
      <dt id="addon_show-hint"><a href="../addon/hint/show-hint.js"><code>hint/show-hint.js</code></a></dt>
      <dd>Provides a framework for showing autocompletion hints.
      Defines <code>CodeMirror.showHint</code>, which takes a
      CodeMirror instance and a hinting function, and pops up a widget
      that allows the user to select a completion. Hinting functions
      are function that take an editor instance, and return
      a <code>{list, from, to}</code> object, where <code>list</code>
      is an array of strings (the completions), and <code>from</code>
      and <code>to</code> give the start and end of the token that is
      being completed. Depends
      on <code>addon/hint/show-hint.css</code>. See the other files in
      the <a href="../addon/hint/"><code>addon/hint</code></a> for
      hint sources for various languages. Check
      out <a href="../demo/complete.html">the demo</a> for an
      example.</dd>
      <dt id="addon_match-highlighter"><a href="../addon/search/match-highlighter.js"><code>match-highlighter.js</code></a></dt>
      <dd>Adds a <code>highlightSelectionMatches</code> option that
      can be enabled to highlight all instances of a currently
      selected word.
      Demo <a href="../demo/matchhighlighter.html">here</a>.</dd>
      <dt id="addon_lint"><a href="../addon/lint/lint.js"><code>lint/lint.js</code></a></dt>
      <dd>Defines an interface component for showing linting warnings,
      with pluggable warning sources
      (see <a href="../addon/lint/json-lint.js"><code>json-lint.js</code></a>
      and <a href="../addon/lint/javascript-lint.js"><code>javascript-lint.js</code></a>
      in the same directory). Defines a <code>lintWith</code> option
      that can be set to a warning source (for
      example <code>CodeMirror.javascriptValidator</code>). Depends
      on <code>addon/lint/lint.css</code>. A demo can be
      found <a href="../demo/lint.html">here</a>.</dd>
      <dt id="addon_mark-selection"><a href="../addon/selection/mark-selection.js"><code>selection/mark-selection.js</code></a></dt>
      <dd>Causes the selected text to be marked with the CSS class
      <code>CodeMirror-selectedtext</code> when the <code>styleSelectedText</code> option
      is enabled. Useful to change the colour of the selection (in addition to the background),
      like in <a href="../demo/markselection.html">this demo</a>.</dd>
      <dt id="addon_active-line"><a href="../addon/selection/active-line.js"><code>selection/active-line.js</code></a></dt>
      <dd>Defines a <code>styleActiveLine</code> option that, when enabled,
      gives the wrapper of the active line the class <code>CodeMirror-activeline</code>, 
      and adds a background with the class <code>CodeMirror-activeline-background</code>.
      is enabled. See the <a href="../demo/activeline.html">demo</a>.</dd>
      <dt id="addon_closetag"><a href="../addon/edit/closetag.js"><code>edit/closetag.js</code></a></dt>
      <dd>Provides utility functions for adding automatic tag closing
      to XML modes. See
      the <a href="../demo/closetag.html">demo</a>.</dd>
      <dt id="addon_loadmode"><a href="../addon/mode/loadmode.js"><code>mode/loadmode.js</code></a></dt>
      <dd>Defines a <code>CodeMirror.requireMode(modename,
      callback)</code> function that will try to load a given mode and
      call the callback when it succeeded. You'll have to
      set <code>CodeMirror.modeURL</code> to a string that mode paths
      can be constructed from, for
      example <code>"mode/%N/%N.js"</code>—the <code>%N</code>'s will
      be replaced with the mode name. Also
      defines <code>CodeMirror.autoLoadMode(instance, mode)</code>,
      which will ensure the given mode is loaded and cause the given
      editor instance to refresh its mode when the loading
      succeeded. See the <a href="../demo/loadmode.html">demo</a>.</dd>
      <dt id="addon_continuecomment"><a href="../addon/edit/continuecomment.js"><code>edit/continuecomment.js</code></a></dt>
      <dd>Adds an <code>continueComments</code> option, which can be
      set to true to have the editor prefix new lines inside C-like
      block comments with an asterisk when Enter is pressed. It can
      also be set to a string in order to bind this functionality to a
      specific key..</dd>
      <dt id="addon_placeholder"><a href="../addon/display/placeholder.js"><code>display/placeholder.js</code></a></dt>
      <dd>Adds a <code>placeholder</code> option that can be used to
      make text appear in the editor when it is empty and not focused.
      Also gives the editor a <code>CodeMirror-empty</code> CSS class
      whenever it doesn't contain any text.
      See <a href="../demo/placeholder.html">the demo</a>.</dd>
    </dl>

    <h2 id="modeapi">Writing CodeMirror Modes</h2>

    <p>Modes typically consist of a single JavaScript file. This file
    defines, in the simplest case, a lexer (tokenizer) for your
    language—a function that takes a character stream as input,
    advances it past a token, and returns a style for that token. More
    advanced modes can also handle indentation for the language.</p>

    <p id="defineMode">The mode script should
    call <code>CodeMirror.defineMode</code> to register itself with
    CodeMirror. This function takes two arguments. The first should be
    the name of the mode, for which you should use a lowercase string,
    preferably one that is also the name of the files that define the
    mode (i.e. <code>"xml"</code> is defined in <code>xml.js</code>). The
    second argument should be a function that, given a CodeMirror
    configuration object (the thing passed to
    the <code>CodeMirror</code> function) and an optional mode
    configuration object (as in
    the <a href="#option_mode"><code>mode</code></a> option), returns
    a mode object.</p>

    <p>Typically, you should use this second argument
    to <code>defineMode</code> as your module scope function (modes
    should not leak anything into the global scope!), i.e. write your
    whole mode inside this function.</p>

    <p>The main responsibility of a mode script is <em>parsing</em>
    the content of the editor. Depending on the language and the
    amount of functionality desired, this can be done in really easy
    or extremely complicated ways. Some parsers can be stateless,
    meaning that they look at one element (<em>token</em>) of the code
    at a time, with no memory of what came before. Most, however, will
    need to remember something. This is done by using a <em>state
    object</em>, which is an object that is always passed when
    reading a token, and which can be mutated by the tokenizer.</p>

    <p id="startState">Modes that use a state must define
    a <code>startState</code> method on their mode object. This is a
    function of no arguments that produces a state object to be used
    at the start of a document.</p>

    <p id="token">The most important part of a mode object is
    its <code>token(stream, state)</code> method. All modes must
    define this method. It should read one token from the stream it is
    given as an argument, optionally update its state, and return a
    style string, or <code>null</code> for tokens that do not have to
    be styled. For your styles, you are encouraged to use the
    'standard' names defined in the themes (without
    the <code>cm-</code> prefix). If that fails, it is also possible
    to come up with your own and write your own CSS theme file.<p>

    <p id="StringStream">The stream object that's passed
    to <code>token</code> encapsulates a line of code (tokens may
    never span lines) and our current position in that line. It has
    the following API:</p>

    <dl>
      <dt><code>eol() → boolean</code></dt>
      <dd>Returns true only if the stream is at the end of the
      line.</dd>
      <dt><code>sol() → boolean</code></dt>
      <dd>Returns true only if the stream is at the start of the
      line.</dd>

      <dt><code>peek() → character</code></dt>
      <dd>Returns the next character in the stream without advancing
      it. Will return an <code>null</code> at the end of the
      line.</dd>
      <dt><code>next() → character</code></dt>
      <dd>Returns the next character in the stream and advances it.
      Also returns <code>null</code> when no more characters are
      available.</dd>

      <dt><code>eat(match) → character</code></dt>
      <dd><code>match</code> can be a character, a regular expression,
      or a function that takes a character and returns a boolean. If
      the next character in the stream 'matches' the given argument,
      it is consumed and returned. Otherwise, <code>undefined</code>
      is returned.</dd>
      <dt><code>eatWhile(match) → boolean</code></dt>
      <dd>Repeatedly calls <code>eat</code> with the given argument,
      until it fails. Returns true if any characters were eaten.</dd>
      <dt><code>eatSpace() → boolean</code></dt>
      <dd>Shortcut for <code>eatWhile</code> when matching
      white-space.</dd>
      <dt><code>skipToEnd()</code></dt>
      <dd>Moves the position to the end of the line.</dd>
      <dt><code>skipTo(ch) → boolean</code></dt>
      <dd>Skips to the next occurrence of the given character, if
      found on the current line (doesn't advance the stream if the
      character does not occur on the line). Returns true if the
      character was found.</dd>
      <dt><code>match(pattern, consume, caseFold) → boolean</code></dt>
      <dd>Act like a
      multi-character <code>eat</code>—if <code>consume</code> is true
      or not given—or a look-ahead that doesn't update the stream
      position—if it is false. <code>pattern</code> can be either a
      string or a regular expression starting with <code>^</code>.
      When it is a string, <code>caseFold</code> can be set to true to
      make the match case-insensitive. When successfully matching a
      regular expression, the returned value will be the array
      returned by <code>match</code>, in case you need to extract
      matched groups.</dd>

      <dt><code>backUp(n)</code></dt>
      <dd>Backs up the stream <code>n</code> characters. Backing it up
      further than the start of the current token will cause things to
      break, so be careful.</dd>
      <dt><code>column() → integer</code></dt>
      <dd>Returns the column (taking into account tabs) at which the
      current token starts.</dd>
      <dt><code>indentation() → integer</code></dt>
      <dd>Tells you how far the current line has been indented, in
      spaces. Corrects for tab characters.</dd>

      <dt><code>current() → string</code></dt>
      <dd>Get the string between the start of the current token and
      the current stream position.</dd>
    </dl>

    <p id="blankLine">By default, blank lines are simply skipped when
    tokenizing a document. For languages that have significant blank
    lines, you can define a <code>blankLine(state)</code> method on
    your mode that will get called whenever a blank line is passed
    over, so that it can update the parser state.</p>

    <p id="copyState">Because state object are mutated, and CodeMirror
    needs to keep valid versions of a state around so that it can
    restart a parse at any line, copies must be made of state objects.
    The default algorithm used is that a new state object is created,
    which gets all the properties of the old object. Any properties
    which hold arrays get a copy of these arrays (since arrays tend to
    be used as mutable stacks). When this is not correct, for example
    because a mode mutates non-array properties of its state object, a
    mode object should define a <code>copyState</code> method,
    which is given a state and should return a safe copy of that
    state.</p>

    <p id="indent">If you want your mode to provide smart indentation
    (through the <a href="#indentLine"><code>indentLine</code></a>
    method and the <code>indentAuto</code>
    and <code>newlineAndIndent</code> commands, to which keys can be
    <a href="#option_extraKeys">bound</a>), you must define
    an <code>indent(state, textAfter)</code> method on your mode
    object.</p>

    <p>The indentation method should inspect the given state object,
    and optionally the <code>textAfter</code> string, which contains
    the text on the line that is being indented, and return an
    integer, the amount of spaces to indent. It should usually take
    the <a href="#option_indentUnit"><code>indentUnit</code></a>
    option into account. An indentation method may
    return <code>CodeMirror.Pass</code> to indicate that it
    could not come up with a precise indentation.</p>

    <p id="electricChars">Finally, a mode may define
    an <code>electricChars</code> property, which should hold a string
    containing all the characters that should trigger the behaviour
    described for
    the <a href="#option_electricChars"><code>electricChars</code></a>
    option.</p>

    <p>So, to summarize, a mode <em>must</em> provide
    a <code>token</code> method, and it <em>may</em>
    provide <code>startState</code>, <code>copyState</code>,
    and <code>indent</code> methods. For an example of a trivial mode,
    see the <a href="../mode/diff/diff.js">diff mode</a>, for a more
    involved example, see the <a href="../mode/clike/clike.js">C-like
    mode</a>.</p>

    <p>Sometimes, it is useful for modes to <em>nest</em>—to have one
    mode delegate work to another mode. An example of this kind of
    mode is the <a href="../mode/htmlmixed/htmlmixed.js">mixed-mode HTML
    mode</a>. To implement such nesting, it is usually necessary to
    create mode objects and copy states yourself. To create a mode
    object, there are <code>CodeMirror.getMode(options,
    parserConfig)</code>, where the first argument is a configuration
    object as passed to the mode constructor function, and the second
    argument is a mode specification as in
    the <a href="#option_mode"><code>mode</code></a> option. To copy a
    state object, call <code>CodeMirror.copyState(mode, state)</code>,
    where <code>mode</code> is the mode that created the given
    state.</p>

    <p id="innerMode">In a nested mode, it is recommended to add an
    extra methods, <code>innerMode</code> which, given a state object,
    returns a <code>{state, mode}</code> object with the inner mode
    and its state for the current position. These are used by utility
    scripts such as the <a href="#addon_closetag">tag closer</a> to
    get context information. Use the <code>CodeMirror.innerMode</code>
    helper function to, starting from a mode and a state, recursively
    walk down to the innermost mode and state.</p>

    <p>To make indentation work properly in a nested parser, it is
    advisable to give the <code>startState</code> method of modes that
    are intended to be nested an optional argument that provides the
    base indentation for the block of code. The JavaScript and CSS
    parser do this, for example, to allow JavaScript and CSS code
    inside the mixed-mode HTML mode to be properly indented.</p>

    <p>It is possible, and encouraged, to associate your mode, or a
    certain configuration of your mode, with
    a <a href="http://en.wikipedia.org/wiki/MIME">MIME</a> type. For
    example, the JavaScript mode associates itself
    with <code>text/javascript</code>, and its JSON variant
    with <code>application/json</code>. To do this,
    call <code>CodeMirror.defineMIME(mime, modeSpec)</code>,
    where <code>modeSpec</code> can be a string or object specifying a
    mode, as in the <a href="#option_mode"><code>mode</code></a>
    option.</p>

    <p id="extendMode">Sometimes, it is useful to add or override mode
    object properties from external code.
    The <code>CodeMirror.extendMode</code> can be used to add
    properties to mode objects produced for a specific mode. Its first
    argument is the name of the mode, its second an object that
    specifies the properties that should be added. This is mostly
    useful to add utilities that can later be looked
    up through <a href="#getMode"><code>getMode</code></a>.</p>

</div><div class="rightsmall blk">

    <h2>Contents</h2>

    <ul>
      <li><a href="#overview">Overview</a></li>
      <li><a href="#usage">Basic Usage</a></li>
      <li><a href="#config">Configuration</a></li>
      <li><a href="#events">Events</a></li>
      <li><a href="#keymaps">Keymaps</a></li>
      <li><a href="#styling">Customized Styling</a></li>
      <li><a href="#api">Programming API</a>
        <ul>
          <li><a href="#api_content">Content manipulation</a></li>
          <li><a href="#api_selection">Selection</a></li>
          <li><a href="#api_configuration">Configuration</a></li>
          <li><a href="#api_doc">Document management</a></li>
          <li><a href="#api_history">History</a></li>
          <li><a href="#api_marker">Text-marking</a></li>
          <li><a href="#api_decoration">Widget, gutter, and decoration</a></li>
          <li><a href="#api_sizing">Sizing, scrolling, and positioning</a></li>
          <li><a href="#api_mode">Mode, state, and tokens</a></li>
          <li><a href="#api_misc">Miscellaneous methods</a></li>
          <li><a href="#api_static">Static properties</a></li>
        </ul>
      </li>
      <li><a href="#addons">Add-ons</a></li>
      <li><a href="#modeapi">Writing CodeMirror Modes</a></li>
    </ul>

</div></div>

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